#include <iostream>
#include <vector>
using namespace std;

int main()
{
    vector<uint64_t> dp(91, 0);
    dp[0] = 1;
    dp[1] = 1;
    for (int i = 2; i < dp.size(); ++i)
    {
        dp[i] += dp[i - 1] + dp[i - 2];
    }

    int n = 0;
    while (cin >> n)
    {
        cout << dp[n] << endl;
    }

    return 0;
}